<form method="get" id="searchform" action="<?php bloginfo('home'); ?>/">
  <p>
    <input class="searchtext" type="text" value="" name="s" id="s" />
    <input class="searchbutton" type="image" name="searchsubmit" title="Search" src="<?php bloginfo('stylesheet_directory'); ?>/images/searchbutton.jpg" />
  </p>
</form>